The invention is related to the field of computer networks.
Computer networks may be organized in a manner referred to as an “overlay network”. An overlay network is a logical collection of member network nodes over an underlying or “substrate” network. Overlay networks can improve the design and operation of a wide variety of distributed applications, by providing an abstraction of the underlying network that may be tailored to the needs of the application, along with features and/or tools that support network functions of the application.
Some overlay networks may be formed without consideration of underlying physical network topology, in which case the routing of message in such overlay networks is based on logical topology only. For example, there are known Distributed Hash Table (DHT) based overlay networks that utilize a logical ring topology and conduct routing based on such logical ring. Two neighbors on the logical overlay network could be far away from each other in underlying substrate or physical network. This situation can be viewed as a mismatch between physical network topology and logical topology. Such a mismatch can degrade performance of the overlay network, because routing decisions that are sensible at the logical level may be far from optimal at the physical level. A message traveling straight from one neighbor to the next at the logical layer may be traveling a needlessly long and/or circuitous path in the physical network.
Topology-aware overlay network protocols aim to mitigate mismatch between physical and logical networks. Known protocols include features such as measuring round trip time (RTT) to known landmark nodes and grouping nodes based on similarity of RTTs; measuring node proximities as indicated by RTT values and grouping nodes based on measured RTT values; and use of a synthesized network map to capture underlying physical topology.